The circulating neutrophils have three major tasks that they must accomplish before they can carry out their final task of phagocytosis. First, they must deform and flow through the capillaries often while in a stimulated state. Second, they must recognize sites of inflammation in the post-capillary venules and rapidly attach to these sites by rolling and then firmly adhering to the endothelial cells that line the walls of these venules. Finally, they must migrate through the vessel wall and into the surrounding tissue by a continuous process of adhesion and detachment. Our long term goals seek to address fundamental questions: (1) how neutrophils when stimulated become rigid, aggregate and disaggregate, adhere and detach and migrate; (2) What are the neutrophil's cortical tension and viscosity and how do they change when stimulated and how do these changes influence their ability to move through the small capillaries of the body?; (3) What are the fundamental bond forces between the antigens on the unstimulated and stimulated neutrophils and their ligands and antibodies?